The present invention relates to a hearing aid comprising at least two parts which can be separated and within which a chamber for accommodating a battery is delimited, provided with a microphone, an amplifier that processes the signal originating from the microphone and a loudspeaker, said loudspeaker being connected via a connecting channel to a sound-emitting opening in said hearing aid.
A hearing aid of this type is generally known in the prior art. With such a hearing aid the loudspeaker is some distance away from the sound-emitting opening and a connecting channel to the sound-emitting opening from the loudspeaker is required. Aids of this type are in particular intended to be fitted very deeply in the auditory canal, preferably in such a way that no parts are located outside the auditory canal. With this arrangement the problem arises that secretions from the ear permeate the sound conduit and are able to damage the loudspeaker here. Moreover, if the sound conduit is blocked this has an appreciable adverse effect on the sound quality. Such blockages are particularly difficult to remove and there is a risk that the user will damage the loudspeaker when cleaning the sound conduit. This is one of the reasons why hearing aids of this type which are placed deep in the ear are not yet in general use.
In the prior art it is proposed to fit a filter in the sound-emitting opening. In view of the size of such hearing aids and the size of the sound conduit it is clear that such filters are particularly small and have a very low capacity. Therefore these filters have to be regularly replaced, which is laborious.
According to another proposal developed in the prior art, a non-return valve is arranged in the sound conduit. Various variants of this are known but practice has shown that such valves are both vulnerable and unreliable because these become blocked by the secretions from the ear and then no longer function.